Influence of axial bearing dynamics on rotor vibrations: Transient analysis considering cavitation and coupling of axial and radial fluid films
Final Report Abstract
In addition to the elastic and inertia properties of the rotor as well as the external loads, the vibration behaviour of rotor systems is mainly determined by the bearings. Due to the advantageous mechanical and thermal characteristics as well as the low costs, hydrodynamic bearings are often used. On the one hand, this applies to journal bearings, which dominantly influence the bending vibrations, and at the same time thrust bearings are used to account for axial loads. Due to their respective stiffness and damping parameters, both bearing types significantly contribute to the system behaviour, which has a drastic effect on the resulting vibrations and stability. Continuous advancements and increasing demands require an improved simulation quality of transient system behaviour, which is why detailed modelling of the system properties of the rotor system, bearings and their interactions are necessary. For transient studies, it is not adequately possible to use established steady-state solutions in the field of coupled rotor bearing simulation. While the solution of a non-linear equation system is sufficient for quasi-stationary considerations of the bearing situation, time integrations must be carried out for transient questions with respect to rotor dynamics. A correspondingly detailed consideration of the bearing makes the evaluation of the Reynolds differential equation necessary at each step of the time integration, taking into account the time-variant cavitation state. In the previous project, a modified cavitation algorithm was developed for journal and floating ring bearings based on Elrod’s approach, which was transferred to thrust bearings. In this context, in addition to the simple thrust bearing, various design variants occur, which can be divided into combined bearings, floating disc bearings and tilting pad bearings. Hydraulic couplings between axial and radial lubricating films as well as mechanical couplings to the components of the rotor bearing system under the influence of cavitation were taken into account. The extended simulation model was used to predict relevant vibration phenomena (e.g. subharmonic vibrations or tilting pad flutter).
Publications
- Analysis of dynamical behaviour of full-floating disk thrust bearings. Bulletin of the Polish Academy of Sciences: Technical Sciences, 2021
Steffen Nitzschke, Christian Ziese und Elmar Woschke
(See online at https://doi.org/10.24425/bpasts.2021.139001) - Transient simulation of a rotor supported inpartially filled herringbone grooved journalbearings using the narrow groove theory -boundary conditions. Vibration Engineering for a Sustainable Future, pp. 151–156, 2021
Steffen Nitzschke, Elmar Woschke, Christian Daniel und Thorsten Sporbeck
(See online at https://doi.org/10.1007/978-3-030-46466-0_21)
